This invention relates generally to irrigation sprinklers of the type having a rotatably driven spray head for projecting one or more streams of irrigation water over a surrounding terrain area and associated vegetation. More particularly, this invention relates to an improved reversing gear drive system for reversing the direction of spray head rotation back and forth within the range of a predetermined part-circle arcuate path.
Irrigation sprinklers of the type having a rotatably driven spray head are generally known in the art, wherein the spray head includes at least one spray nozzle through which a stream of irrigation water is projected outwardly to irrigate surrounding terrain and associated vegetation. In such sprinklers, the spray head is rotated about a vertical axis and may be reversibly driven with an oscillating or back and forth motion between adjustably set end limits to sweep the water stream over an arcuate, part-circle terrain area. Rotary drive power is commonly produced by a turbine motor having a water-driven turbine adapted to be driven by some or all of the water flowing through the sprinkler to the spray head. This turbine typically comprises a relatively high speed and relatively low torque device, and provides a rotary input to a reduction gear unit which produces a relatively low speed and relatively high torque output for rotatably driving the spray head.
Within or following this reduction gear unit, a reversing gear mechanism is provided for reversing the direction of spray head rotation. One common means for achieving spray head reversal is disclosed in U.S. Pat. No. 3,107,056, and comprises a shiftable gear carrier including an input drive gear coupled via a suitable number of idler gears to rotatably drive a pair of output gears in opposite directions. This arrangement is commonly referred to as an xe2x80x9codd gearxe2x80x9d or xe2x80x9codd idlerxe2x80x9d system since the number of idler gears associated respectively with the two output gears must differ by an odd number, such as one, to rotatably drive the output gears in opposite directions. The gear carrier is adapted for shifting between a first or forward-drive position with one of the output gears engaging and driving a ring gear or the like coupled to the spray head, and an alternative second or reverse-drive position with the other output gear engaging and driving the ring gear. A toggle or shifting lever on the gear carrier is contacted by a pair of limit stops mounted for rotation with the spray head to shift the gear carrier between the forward-drive and reverse-drive positions. In this manner, the spray head is reversibly rotated to sweep the water stream back and forth over the prescribed part-circle terrain pattern. The arcuate width of the irrigated terrain pattern may be adjustably selected by adjusting the arcuate spacing between the pair of limit stops.
Such reversing gear mechanisms have been subject to undesirable stalling or locking up without proper shifting between the forward-drive and reverse-drive positions. More particularly, since the reversing gear mechanism cannot operate with both output gears simultaneously engaged with the ring gear to drive the spray head, there is an inherent intermediate neutral position during shifting wherein both output gears are at least momentarily disengaged from the ring gear. In an effort to prevent undesirable stalling of the gear carrier in this neutral position, over-center spring arrangements have been provided to load the gear carrier and/or the toggle lever in a manner intended to positively displace the gear carrier through this neutral position.
However, over-center spring arrangements have not been completely successful in eliminating gear carrier stalling. In this regard, spring-loaded displacement of the gear carrier through the neutral position requires a spring force exceeding resistance forces such as frictional resistance attributable to accumulation of dirt and grit between moving parts. The applied spring force for shifting must also exceed reaction forces interacting between each output gear and the ring gear tending to cause those gears to resist disengagement. Whenever the frictional resistance and/or reaction forces exceed the applied spring force for shifting, stalling can occur. Unfortunately, in an over-center spring arrangement, the applied spring force is smallest at the moment of initial shifting displacement of the gear carrier, whereby relatively small resistance forces at this moment of initial gear carrier displacement can therefore cause stalling to occur. Alternative reversing mechanism designs have generally been more complex with additional moving parts, but have not satisfactorily overcome the problem. See, for example, U.S. Pat. Nos. 4,568,024; 4,901,924; 5,673,855; and 4,955,542.
There exists, therefore, a need for an improved reversing mechanism for reversibly driving a spray head in an irrigation sprinkler or the like, wherein the reversing mechanism is not subject to undesirable stalling. The present invention fulfills this need and provides further related advantages.
Based on the foregoing, it is a primary object of the present invention to provide an improved reversing gear drive system.
It is also an object of the present invention to provide an improved reversing gear drive system that virtually eliminates or greatly reduces the risk of stalling when a mechanical shift mechanism displaces through a neutral position to change the direction of rotation.
It is another object of the present invention to provide an improved reversing gear drive system that reduces the number of moving parts in the mechanical shift mechanism.
It is an additional object of the present invention to provide an improved reversing gear drive system that may be adapted to sprinklers and other rotating devices that require a reversal of direction.
It is still anther object of the present invention to provide an improved reversing gear drive system that reduces the number of components and provides more space and greater clearance such as for accommodating a conduit in a sprinkler or the like for carrying water.
It is a further object of the present invention to provide an improved reversing gear drive system that is more reliable and durable in comparison with prior art systems.
In accordance with the invention, an improved reversing gear drive system is provided for use in an irrigation sprinkler or the like, of the type having a rotatably driven spray head for sweeping an outwardly projected stream of irrigation water over a surrounding terrain area and associated vegetation. The reversing gear drive system comprises a gear carrier having first and second output gears driven rotatably in opposite directions. A shift mechanism is provided for shifting the gear carrier between forward-drive and reverse-drive positions with the first and second output gears alternately engaged with a ring gear or the like for rotatably driving the spray head in opposite directions. The shift mechanism includes a shift lever and a reverse trip spring coupled to the gear carrier for engaging arcuately spaced limit stops mounted for rotation with the spray head.
As one of the limit stops rotates into engagement with the shift mechanism, the limit stop initially engages and loads the trip spring to apply a reverse shift force to the shift lever, and then engages and retracts a latch to release the shift lever for spring-loaded gear carrier shifting to reverse the direction of spray head rotation. Upon such reversal, the latch re-engages the shift lever to positionally retain the gear carrier until the opposite limit stop rotates into engagement with the shift mechanism.
In a preferred form, the first and second output gears on the gear carrier are positioned for respective meshed engagement with a ring gear coupled to and rotatably driving the spray head. The limit stops are mounted for rotation with the ring gear, and one or both of the limit stops may be adjustably set to define a predetermined part-circle arcuate path of motion for the spray head. In the preferred form, the latch is spring-loaded to engage and retain the shift lever in the forward-drive or reverse-drive position with the respective one of the first and second output gears in driving engagement with the ring gear. As each limit stop rotates into engagement with the shift mechanism, the limit stop initially engages and loads the reverse trip spring while the latch retains the gear carrier in the set drive position for continued spray head rotation. Thereafter, a ramped cam on the limit stop engages and retracts the latch to a position disengaged from the shift lever to permit the loaded trip spring to displace the shift lever and thereby move the gear carrier through a neutral position to the opposite drive position for rotatably driving the spray head in an opposite rotational direction. Importantly, the magnitude of the torque applied by the reverse trip spring to shift the gear carrier is a maximum at the moment of initial shifting displacement.
In the event that resistance forces such as friction act to resist the desired spring-loaded shifting displacement of the gear carrier upon latch retraction, each limit stop is additionally provided with a stop tab for engaging and initiating movement of the shift lever. Further rotational driving of the spray head subsequent to latch retraction moves the stop tab against the shift lever to positively initiate shifting displacement thereof toward the opposite drive position. As soon as this displacement starts, any resistance forces are overcome and the reverse trip spring drives the gear carrier with a positive action to the opposite drive position.
Other features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.